Trenchless replacement of many types of pipe material can be accomplished using pipe bursting if the pipe material in question is essentially brittle. In pipe bursting, an expander with a diameter larger than an inner diameter of the pipe is forced into the pipe, causing it to fracture into brittle pieces. In some situations, pipe formed from a more ductile material must be replaced. More ductile materials cannot be fractured or burst in a brittle manner due to their ductile properties. Ductile iron, for example is typically split using one or more rotatable cutter wheels that are pulled through the pipe to be replaced. The cutter wheels split a side of the pipe as they are pulled into the pipe.
Although typically classified a either “ductile” or “brittle,” materials such as ductile iron lie on a continuum between brittle and ductile properties. Materials such as ductile iron are still relatively stiff, and their generally thick walled configuration provides significant rigidity during a splitting operation. As an expander or cutter is forced into a pipe having ductile properties, a certain level of axial stiffness is needed to keep the pipe from collapsing upon itself like an accordion if the required rigidity is not present. Therefore, as pipe materials become more ductile, and/or wall thickness becomes thinner, pipe splitting becomes more and more difficult. One example of a pipe configuration that is difficult to split is corrugated pipe such as corrugated steel often used in ditches or elsewhere along roadways.
What is needed is an improved splitter for difficult materials and/or pipe configurations such as thin walled pipe or corrugated pipe.